


sanscest oneshots

by 1_gayperson



Category: Undertale (Video Game)
Genre: Alternate Universe - Dreamtale (Undertale), Alternate Universe - Dusttale (Undertale), Alternate Universe - Errortale (Undertale), Alternate Universe - Inktale (Undertale), Alternate Universe - Underswap (Undertale), Dreamtale Sans (Undertale), Horrortale Sans (Undertale), Other, Underfell Sans (Undertale), Underverse
Language: English
Status: Completed
Published: 2020-05-06
Updated: 2020-05-06
Packaged: 2021-03-02 17:08:54
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 5
Words: 2,524
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24040342
Author URL: https://archiveofourown.org/users/1_gayperson/pseuds/1_gayperson
Summary: uh-i won't post much, but i have some content. i psot more on my wattpad:@/imafuckingaypersonI'll alos take requests if ya have any
Relationships: Sans & Sans (Undertale), Sans (Undertale)/Original Character(s)
Kudos: 12
Collections: Undertale NSFW





	1. Crossmare (Part 1)

**Author's Note:**

> not really anything, lemons/smut and fluff, maybe angst sometimes

Cross slightly groaned, turning over and over in the bedsheets. He just wanted to sleep, but his body apparently was being such a bitch to him and decided that he would be cold. The sheets weren't enough to cover at all, it was s o annoying to him. 

He knew somehow he was going to get Nightmare into his room no matter what. He stood up from the bed, shivering as he only put his fluffy hood on, he put on slippers as well. He walked up to the door, opening it and peering in the dark shadowy corners of the mansion hallways. All he was wearing was his hoodie, shorts and slippers.

He made his way through them, hugging himself. Nightmare was probably in his office, sorting out papers or something. He kept walking, eventually stopping at his door.

Cross looked in, finding Nightmare lock eyes with him. He squeaked, backing away from the door.

Nightmare walked to the door, sighing as his tentacles twitched behind him.  
"What do you want button?" He asked, looking at him.

Cross's face flushed with the nickname, looking away.  
"I-Uh-C-Can you come sleep with me? I-It's kind of cold..." he says, looking down and letting out a small huff.

Nightmare stayed silent for a moment. He walked back into the room, coming out after a few seconds.

"There. Let's go." He says, walking past the oreo as hed grabbed him with his tentacle and took him to their room. 

Cross let out a squeak, but went limp. He knew it would be easier for Nightmare if he just went limp, not struggling.

They arrived in thr room less than three minutes, the goopy skeleton setting the oreo down onto the bed. The taller started to strip.

Cross looked at him, blushing.  
"N-Nightmare- You know you don't have to take off all your clothe-" Nightmare only cut him off, all his clothes being gone from his skeletal form. He didn't have anything formed.

"It's more comfortable if I take them off." He said, climbing onto their bed, and sitting next to Cross.  
"Now you strip."

Cross squeaked at his comment, blushing madly.  
"N-Nightmare! Why-"

"Just do it. It'll only be fair." He said, he tentacles flicking behind him.  
"Or I'll do it."

Cross only looked away, sweat falling from his skull. He stood, his back facing Nightmare. He started to take his hoodie off, then his shorts, then the rest. He looked back at Nightmare, who had a light cyan blush on his face. 

Nightmare smirked, grabbing Cross with his tentacle. He lay on the bed comfortably, setting Cross next to him. 

The taller immediately hugged him, putting his head on Cross's skull and blinking as Cross snuggled into his chest. Nightmare turned off the light with his tentacle, before wrapping them around him and his lover.

Throughout the night, they only stayed next to eachother, only cuddling.


	2. Crossmare (Part 2)

**Summary for the Chapter:**

> part two of the other one anjsjxjd

Nightmare was currently awake, staring at Cross. The other, monochrome skeleton, was calmly asleep, breathing in and out normaly. And, quite cute, in Nightmare's perspective. 

His round, perfect snow white bones, and the red scar under his red glowing eye. Both of his eyes were closed at this time, but Nightmare knew his eyes glowed in some kind of mesmerizing way, and he loved it. He reached his hand out, putting his hand onto the smaller's perfect cheek bone and rubbing his thumb on it. He smiled a bit, blushing a light cyan and he did so.

Cross suddently woke up, furrowing his eyebrows(?) and blinking several times to adjust his eyesight. He blushed a dark lilac, feeling Nightmare's warm hand on his cheek. 

"What are you doing Nigh-" Cross was cut off.

"You're so cute." Nightmare said bluntly, his blush increasing. He kept caressing Cross's cheek, a small smile forming into a bigger one.

Cross's blush was increasing by the seconds.  
"Wha- Nightmare-" he stuttered, huffing as he scotted closer to him.

Nightmare watched him, taking his other hand and putting it on Cross's other cheek. He reached over and kissed the smaller, closing his eye as his cheeks covered in cyan blush.

Cross, who was currently dumbfounded, blushed a dark lilac, kissing Nightmare back immediately. He closed his own mismatched eyes as well.

Nightmare opened his eye, and pulled back, smiling at Cross with his cheeks stained with cyan blush.

Cross opened his eyes and looked at him, smiling as well. It was contagious. Nightmare's wonderful smile, Cross loved it. 

"I love you." Cross said, giving Nightmare kiss on both of his cheeks. He giggled, smiling widely, happy.

Nightmare gave him multiple kisses on his face, smiling, happy as well. 

Cross giggled when he did that.

Nightmare rubbed his cheeks once again.  
"I love you too."


	3. Crossmare angst uwu

**Summary for the Chapter:**

> this is- 
> 
> kinda a vent amdjdjjej

Cross sobbed, gripping onto his pillow tightly. He tried his hardst to stop crying, to stop the tears coming out of his eyes. He didn't want to cry, he didn't want to act like such a fucking cunt. He wanted to be fine, and not burst into tears when something bad happened to him.

He loved Nightmare. But of course, the other didn't. It was fine. He was a just a toy anyway, a toy for Nightmare to feed off of. The tears and sadness he gave off where just more power for Nightmare. It didn't matter. Nothing did. He still continued to live his shity life as Nightmare's guard and second his command.

The place didn't mean anything, once you think about it. The taller didn't care, he only cared about the power he received. 

So, here was Cross, balling his eyes out because of Nightmare. And Nightmare, you ask? Oh, he was having a good time in his room

///--///

Nightmare was on his bed, reading a book silently, feeding off of the negativity from his "teammates" and "family" they called each other. For Nightmare? Nightmare didn't like those words. 

Those words were just lies, words that mean nothing. He didn't care. Did he?

He only feed off of Cross's heartbreak and sobbing, Horror's panics in his room. Dust's insanity and crying. Killer's raidiating negative energy. Error's hatred for everything. It was fine. Fine for him. Fine, what he thiught everyone and everything was.

Fine.

That's what Cross wanted to be.


	4. Crossmare (smut--)

**Summary for the Chapter:**

> they fuck.
> 
> cross ans nightmare.

Nightmare pulled back from Cross, smirking. His hands were either side of the other's face, resting on a wall.  
Cross was drooling and in a daze.

"Mhm, Nighty~..." Cross moaned quietly. Nightmare chuckled, putting a hand under his shirt, rubbing his ribs. Cross jolted, his eyes going lidded as his legs felt like jelly. He summoned an ecto-body, his clothes going skin-tight.

Nightmare kissed him again, roughly putting his tounge in Cross's mouth and sucking on it. He let out a squeak, blushing as he gripped Nightmare's jacket. The taller grabbed his hips, tilting his head to get more inside the other's mouth, his tongue tugging on the others. Cross let out cute mewls, grabbbing Nightmare's shoulders, pulling him closer. Nightmare had his tongue swirling all over Cross's mouth, slowly stripping his clothes and the other's off with his tentacles.

Nightmare broke the kiss to get Cross's shirt off, doing the same to his turtleneck. He kissed him again roughly after.

He slid his own shorts off, slipping off Cross's more slower. Cross let out a whine in the kiss, pulling away from it.

"Mhm, c-come on N-Nighty~" he said, drooling and he bit his lower lip. "P-pound into me u-until y-you can't a-anymore~..." he purred, griding against him as his shorts slid off.

Nightmare blushed, grinning at him. He positioned at his entrance, his tip rubbing the Cross's entrance. The smol whined, pushing himself towards him. Nightmare moved his hips back.

"Nu-uh, don't do anything by yourself, love." He said, "..or maybe I'd just leave you here to take care of your own self..." he purred, Cross only whined.

Nightmare smirked, thrusting into Cross harshly. Cross only moaned, letting out mewls and squeals as he was pounded on. Nightmare was going as dast as he could, trying to hit a certain spot. Cross moaned loudly when Nightmare hit a part, causing the taller to pound that spot repeatedly. Cross moaned louder, drooling as his eye lights went to the back of his skull.

"Hm, you're enjoying this, aren't you sweetheart?" He asked, Cross only gripped his shoulder, pressing against him. Nightmare took Cross's legs, putting them on his shoulders to get a better acces to his good spot.   
Cross squezzed his eyes shut, "Ngh~...N-nighty, I-I'm close~" he breathed, moaning loudly as he cummed. Nightmare kept going, Cross's moans becoming more louder.  
"hAHHhh~" Nightmare finay came inside the other, pulling out. The other panted. Nightmare carried him to the nearby bed, setting him on it. Nightmare lay down next to him, pulling the covers over him and Cross.   
"I love you, Nighty~" Cross purred, panting and he snuggled up to Nightmare.   
Nightmare grinnedz nuzzling the other affectionately.   
"I love you too, Crossy."


	5. Crossmare (Again)

**Summary for the Chapter:**

> cross and nm meet uwu

Cross walked around the park, smiling. He was eating a chocolate. Spotting a bench, he sat down on it. 

He closed his eyes, feeling the cool breeze pass by. The colored trees shaking slightly as leaves lightly fell down from the trees.

Fall, such a beautiful season.

Finishing the chocolate, he threw the wrapper in the trash can by him, like good boi.

-

Nightmare growled, sitting on a bench by a Black and White skeleton. He looked away, not really wanting to socialize with them.

He was waiting for his friends group, Horror, Dust, Killer, and Error.

They had changed the time they were going to meet up, and Nightmare was too lazy to go back home. So he told them that he'll just wait for them in the Park, in a bench by himself. 

Killer said he was excited, obviously, because, well, he was his boyfriend.

Right as he hung up, a black and white skeleton sat on the bench he was going to sit at. Grunting, he went to sit on it. The others had ducks surrounding it, or there where couple's sitting there. Minimum bench number was five.

-

Cross looked over at the person who sat down. He smiled, blushing slightly. 

"Hi! I've never seen you before! Who are you?" He asked in ethuastic voice.

Nightmare looked over at the smol, frowning.

"How." He said bluntly. He blushed slightly of embarrassment, "I mean, uh...Why are you talking to me?" Nightmare asked, looking away from the monochrome skeleton. 

"Oh! Uh...I don't know...?" He said, putting his index finger by his mouth, "But hey, What's your name?" Cross said, raising his hand up to him to shake his hand

"I-.....Uh....Nightmare...." The goopy skeleton replied, looking at Cross's hand before scowling. 

"I don't do handshakes." He said, glaring at Cross. Cross just stared at him, his smile disappearing. It returned back to its place.

"Well, uh....Why are you doing here? You look like someone who would be stuck up inside," Cross said, slightly laughing. Cyan blush rose from Nightmare's cheeks.

"I-...." He stayed silent, " It's my choice if I want to hang out with friends..." He said, closing his eye. 

"Do you want to be friends?" Cross asked, smiling happily. 

"Sure." Nightmare said bluntly, he slapped himself mentally for that one. Again, saying things without thinking it through.

Cross beamed, laughing. "Ok!"

They sat there in silence.

"So how are your other friends like?" Cross asked, excited to meet Nightmare's possibly edgy friends.

"Well, there's Horror." Nightmare said.

"He likes meat. A lot. And sluts, apparently, too." He said, raising a finger.

"O-oh..." Cross quietly said.

"I'm just kidding, damn. We used to call his boyfriend a slut because he wore revealing shit, but then we stopped when Horror told us some not so pleasant things that happened to him." Nightmare finished, "He also would kill someone. He doesn't though. And he also loves cooking, even though he's semi-bad at it." 

"Okay..."

"Then there's Dust. God, I swear. He's annoying. All of them are. But annoying as in a memey way. A good way." Nightmare explained. "His brother also died, so don't mention him around Dust. He'll beat the living crap out of you."

"How do you know that?"

"He did it to some dude in High School."

"Oh."

"I know, tragic." Nightmare thought for a short moment. Why is he telling this skeleton this? He shook it off, enjoying Cross's company.

"There's also Error. A glitch, but a good glitch. He likes destroying shit. Hell, he even destroyed Dust's old shack. Good thing he doesn't live there no more, though. He also has a love interest, Ink."

Nightmare kept on talking about his brother and the star Sanses. He almost forgot someone. 

Killer.

"Oh, and my boyfriend Killer. Almost forgot." he says, blinking.

"Honestly, I just started dating him because he kept on begging me. I eventually gave in. Wish I didn't." he said, "I can't get rid of him now, he's fucking annoying, I can't even."

Cross stared at Nightmare. He's kinda hot. Cross kept wondering the things they could do together, maybe even be together...

A nearby voice was heard.

"HEY NIGHTMARE! 'WHACHA GOT THERE?"

It was a skeleton, a dark one.

He wore a black coat, with a red shirt under. His blue scarf was slightly moving to where the cold air was coming from, the dark shade of blue being a whole lot different to the Fall colored leaves. His eyes were mismatched, and tear like marks traveled down his cheeks. He had sweat like pants on, one of them being rolled up to his knee while the other by his ankle. He wore black slippers. His fingers were yellow and red. Waving at Nightmare, he walked over with other skeletons behind him.

One looked like a maniac, red glowing eye was big and imitading. A crack on his skull was visible, a hole left on it. He wore a jacket, the hood being filled with fluff like Cross, only it wasn't that much. He also wore a light gray shirt under the dark light blue jacket. A grin spread across his face. Black shorts with white stripes were on him, along with dark light pink slippers, pure white socks visible.

Another had his hood on. His eyes were mismatched, such as the first one with dark bones. Only his were white, and his fashion sense was different. He wore a blue jacket, a lot like the previous, only he didn't have fluff, only a gray hood coming from the blue jacket. He had a white shirt under it, and Black shorts with sneakers on.

This one he could recognize as Killer. Why? He came over and hugged Nightmare, slightly squealing, "Nighty!" Cross looked away, huffing.

Killer wore the same as the others, only the clothing a bit lighter. He had sneakers on too but they were gray ones, unlike one of the other's white ones. His eyes were pure black, with substance leaking out of them a smile was formed on his face with a gray tint of blush.

Cross didn't like Killer at first glance.


End file.
